Yggdrasil'

The ash-tree, whose roots run in three directions: one to the
Asa-gods in heaven, one to the Frostgiants, and the third to the
under-world. Under each root is a fountain of wonderful virtues. In
the tree, which drops honey, sit an eagle, a squirrel, and four stags.
At the root lies the serpent Nithhöggr gnawing it,
while the squirrel Ratatöggr runs up and down to sow strife between
the eagle at the top and the serpent. (Scandinavian mythology.)